Luminescent device and manufacturing method for luminescent device and semiconductor device

ABSTRACT

A luminescent device and a manufacturing method for the luminescent device and a semiconductor device which are free from occurrence of cracks in a compound semiconductor layer due to the internal stress in the compound semiconductor layer at the time of chemical lift-off. The luminescent device manufacturing method includes forming a device region on part of an epitaxial substrate through a lift-off layer; forming a sacrificing portion, being not removed in a chemical lift-off step, around device region on epitaxial substrate; covering epitaxial substrate and semiconductor layer and forming a covering layer such that level of surface thereof in the region away from device region is lower than luminescent layer surface; removing covering layer on semiconductor layer, and that on sacrificing portion surface; forming a reflection layer on covering layer surface and semiconductor layer surface; and forming a supporting substrate by providing plating on reflection layer.

This is a Division of application Ser. No. 13/978,677 filed Jul. 8,2013, which is a National Phase of Application No. PCT/JP2012/050363filed Jan. 11, 2012, which claims priority to Japanese PatentApplication No. 2011-007083 filed Jan. 17, 2011. The disclosure of theprior applications are hereby incorporated by reference herein in theirentireties.

BACKGROUND

1. Technical Field

The present invention relates to a luminescent device and amanufacturing method for the luminescent device and a semiconductordevice, and particularly relates to a luminescent device having astructure in which a p-type semiconductor layer and an n-typesemiconductor layer are laminated on a supporting portion and amanufacturing method therefor.

2. Background Art

Group III nitride semiconductors have a wide band gap, and therefore,they are widely used as materials for luminescent devices, such as blue,green, and other color LEDs (light-emitting diodes), LDS (laser diodes),and the like. Such luminescent devices are configured by laminating ap-type semiconductor layer (p-type layer) and an n-type semiconductorlayer (n-type layer) by the epitaxial growth process.

In order to manufacture such a structure with a good quality beingprovided at a low cost, a p-type layer and an n-type layer areepitaxially grown on an epitaxial substrate made of a material otherthan the group III nitride semiconductor in general. In this case, thetype of material which can be used as an epitaxial substrate forobtaining a semiconductor layer with a particularly good quality islimited. For example, gallium nitride (GaN), a typical group III nitridesemiconductor, can be grown on a dissimilar epitaxial substrate formedof SiC, sapphire, or the like, by the MOCVD (Metal Organic ChemicalVapor Deposition) process, the HVPE (Hydride Vapor Phase Epitaxy)process, or the like.

However, since sapphire is an insulator, it is required to provide twoelectrodes on the top face of a semiconductor layer laminated thereon,which has caused problems that the effective luminescent area isnarrowed down for a given substrate area, in comparison with theconductive substrate, and both electrodes being provided on the sameface locally increases the current density, resulting in the devicebeing deteriorated due to the heat generated.

Then, in Patent Document 1, there is disclosed a method formanufacturing a luminescent device utilizing the laser lift-offtechnology, and in Patent Document 2, there is disclosed a method formanufacturing a luminescent device utilizing the chemical lift-offtechnology. With these manufacturing methods, an n-type layer, a p-typelayer, and a p-side electrode are sequentially formed on a sapphiresubstrate, which is followed by newly forming a conductive supportingsubstrate on the side of the p-side electrode, and peeling-off thesapphire substrate.

With a vertical type luminescent device based on such a lift-offtechnology, a supporting substrate made of another material which isoptimized in thermal conductivity, and the like, can be used, whereby ahigh heat dissipation and reliability can be obtained.

CITATION LIST Patent Literature

Patent Document 1

Japanese Unexamined Patent Application Publication No, 2008-53685

Patent Document 2

Domestic Re-publication of PCT International Application No. 2006-126330

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The chemical lift-off technology is excellent in productivity and lessdamage to the luminescent layer, as compared to the laser lift-offtechnology. However, unlike the laser lift-off technology, the chemicallift-off technology requires that, at the time of peeling off thecompound semiconductor layer forming a luminescent device from theepitaxial substrate, an etchant be supplied to the lift-off layer foretching the lift-off layer from the circumference thereof where theetchant is brought into contact therewith. Therefore, it has been foundthat a problem is presented that, during gradual peeling-off thelift-off layer from the compound semiconductor layer, cracks areinitiated in the compound semiconductor layer, resulting from theinternal stress generated by the difference in lattice constant andthermal expansion coefficient between the dissimilar epitaxial substrateand the compound semiconductor layer at the time of growth beingconcentrated in the portion which has not yet been peeled off.

In view of the aforementioned problem, it is an object of the presentinvention to provide a luminescent device and a manufacturing method fora semiconductor device including the luminescent device which are freefrom occurrence of cracks in a compound semiconductor layer due to theinternal stress in the compound semiconductor layer at the time ofchemical lift-off.

Means for Solving the Problems

In order to achieve the aforementioned object, the luminescent deviceand the manufacturing method for the luminescent device and thesemiconductor device in accordance with the present invention areconfigured as follows.

The first manufacturing method for a semiconductor device (correspondingto claim 1) is a manufacturing method for a semiconductor device,comprising: a device region formation step of forming a device regionconstituted by a semiconductor layer on part of an epitaxial substratethrough a lift-off layer; a sacrificing portion formation step offorming a sacrificing portion, being not removed in a later-mentionedchemical lift-off step, around the device region on the epitaxialsubstrate; a covering step of forming a covering layer, covering theepitaxial substrate except part on the semiconductor and on thesacrificing layer; a foundation layer formation step of forming afoundation layer on a surface on the epitaxial substrate including parton the semiconductor and on the sacrificing layer and a covering layersurface; a plating step of forming a supporting substrate by providingplating on the foundation layer; a covering layer removing step ofdissolution removing of the covering layer; a chemical lift-off step ofseparating between the semiconductor layer and the epitaxial substrateby dissolution removing of the lift-off layer; and a sacrificing portionremoving step of separating between the epitaxial substrate and thefoundation layer at the sacrificing portion after the chemical lift-offstep.

The first manufacturing method for a luminescent device (correspondingto claim 2) is a manufacturing method for a luminescent device includinga semiconductor layer having a luminescent layer, comprising: a deviceregion formation step of forming a device region constituted by thesemiconductor layer on part of an epitaxial substrate through a lift-offlayer; a sacrificing portion formation step of forming a sacrificingportion, being not removed in a later-mentioned chemical lift-off step,around the device region on the epitaxial substrate; a covering step offorming a covering layer, covering the epitaxial substrate except parton the semiconductor and on the sacrificing layer; a foundation layerformation step of forming a foundation layer on a surface on theepitaxial substrate including part on the semiconductor and on thesacrificing layer and a covering layer surface; a plating step offorming a supporting portion by providing plating on the foundationlayer; a covering layer removing step of dissolution removing of thecovering layer; a chemical lift-off step of separating between thesemiconductor layer and the epitaxial substrate by dissolution removingof the lift-off layer; and a sacrificing portion removing step ofseparating between the epitaxial substrate and the foundation layer atthe sacrificing portion after the chemical lift-off step.

The second manufacturing method for a luminescent device (correspondingto claim 3) is the aforementioned method, wherein preferably, in thedevice region formation step, the semiconductor layer includes an n-typelayer, a luminescent layer, and a p-type layer, being constituted by agroup III nitride semiconductor, in this order from the epitaxialsubstrate side.

The third manufacturing method for a luminescent device (correspondingto claim 4) is the aforementioned method, wherein preferably, in thecovering step, a photoresist is coated for making a covering such thatthe level of the covering layer surface from the epitaxial substrate atleast on the sacrificing portion is lower than the luminescent layer,and part of the covering layer on the semiconductor layer and thesacrificing portion is removed by photolithography.

The fourth manufacturing method for a luminescent device (correspondingto claim 5) is the aforementioned method, wherein preferably, in thefoundation layer formation step, the foundation layer includes areflection layer on the semiconductor layer side.

The first luminescent device (corresponding to claim 6) is a luminescentdevice manufactured by any one of the aforementioned first to fourthmanufacturing methods for a luminescent device.

The second luminescent device (corresponding to claim 7) is aluminescent device having a semiconductor layer including a luminescentlayer on a supporting substrate, the supporting substrate having aconcave shape, the semiconductor layer being connected to the bottom ofthe concave shape through a foundation layer, and the supportingsubstrate having a discontinuously independent convex portionconstituted by the foundation layer at the summit of the concave shape.

The third luminescent device (corresponding to claim 8) is a luminescentdevice having the aforementioned configuration, wherein preferably theleakage current flowing when a reverse voltage of 10 volts is applied isless than 10 μA.

Advantages of the Invention

In accordance with the present invention, there can be provided aluminescent device and a manufacturing method for the luminescent deviceand a semiconductor device which are free from occurrence of cracks inthe compound semiconductor layer due to the internal stress between theepitaxial substrate and the compound semiconductor layer at the time ofchemical lift-off.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (a) to FIG. 1(b) are sectional views of a luminescent deviceaccording to the present embodiment of the present invention;

FIG. 2 is a flowchart showing the steps of manufacturing a luminescentdevice according to the present embodiment of the present invention;

FIG. 3 (a) to FIG. 3(f) are sectional views of a substrate in therespective steps of the method for manufacturing a luminescent deviceaccording to the present embodiment of the present invention;

FIG. 4(g) to FIG. 4(i) are sectional views of a substrate in therespective steps of the method for manufacturing a luminescent deviceaccording to the present embodiment of the present invention; and

FIG. 5 is an electron microscope photograph taken in the observation ofthe surface of a compound semiconductor layer on the supportingsubstrate side after the sacrificing layer removing step according tothe present embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment (Example) of the present inventionwill be explained with reference to the accompanying drawings.

FIG. 1 (a) is a sectional view of a luminescent device according to thepresent embodiment of the present invention, FIG. 1 (b) being a top viewof the same. A luminescent device 40 has a configuration in which asemiconductor layer 11 including a luminescent layer 11 b is supportedby a supporting substrate 12. In the luminescent device 40, thesupporting substrate 12 is formed by plating. The supporting substrate12 is concave shaped, a concave portion 13 comprised of a flat bottomface (flat portion) 13 a and a tapered side face 13 b being formedthereon, and on the surface thereof, a reflection layer 14 b beingformed. Further, the semiconductor layer 11 of the luminescent device 40is placed on the flat portion 13 a, and is formed such that the level ofthe surface of a foundation layer 14 in the region away from the flatportion 13 a is higher than the luminescent layer 11 b. Thereby, thelight having reached the side face 13 b from the luminescent layer 11 bis reflected by the reflection layer 14 b, thereby being provided with acomponent which is emitted in a normal line direction of the flatportion 13 a. Furthermore, this luminescent device 40 has a convexportion 41 which is part of the side face 13 b, being formed by thefoundation layer 14, in a location which provides a summit of theconcave portion 13. This convex portion 41 is a columnar portion whichmaintained bonding by means of a sacrificing portion in the chemicallift-off process.

The semiconductor layer 11 of the luminescent device 40 includes theluminescent layer 11 b between an n-type GaN layer (n-type semiconductorlayer: n-type layer) 11 a and a p-type GaN layer (p-type semiconductorlayer: p-type layer) 11 c. On the p-type GaN layer 11 c, a p-sideelectrode 23 is formed.

The supporting substrate 12 of the luminescent device 40 is formed by,for example, Ni plating or Cu plating. In addition, in FIG. 1 (a), aseed layer 14 a for use in forming the supporting substrate 12 is shown.As the seed layer 14 a, which is on the plating side of the foundationlayer 14, palladium (Pd) is used for Ni plating, while, for Cu plating,platinum (Pt)/cupper (Cu) is used.

As the reflection layer 14 b of the luminescent device 40, it ispreferable to use rhodium or ruthenium. This is because rhodium orruthenium has a high reflectivity for the wavelength region of a groupIII nitride, and is hard to be etched by an etchant for chemicallift-off.

According to the aforementioned configuration, the luminescent device 40allows the light having reached to the side face 13 b from theluminescent layer 11 b to be reflected by the reflection layer 14 b andthe convex portion 41, thereby being provided with a component which isemitted in a normal line direction of the flat portion 13 a, whereby thelight can be taken out sufficiently effectively; contrarily to this, inthe case where a conventional flat supporting substrate is used, thelight emitted from the luminescent layer in a lateral direction leakslaterally, thereby the light cannot be taken out with a sufficienteffectiveness.

In addition, unlike a structure which provides a reflection portion in aside direction of the semiconductor layer through an insulating film ona conventional supporting substrate, the luminescent device 40 accordingto the present embodiment has a configuration which provides thereflection layer 14 directly on the supporting substrate 12 not throughan insulating film on the supporting substrate 12. Thereby, theluminescent device 40 is simple in construction, and as explained below,can be easily manufactured.

Hereinbelow, the manufacturing method for the luminescent device 40according to the present embodiment of the present invention will beexplained. The n-type or p-type semiconductor layer 11 used in thisluminescent device 40 can be obtained by epitaxially growing it on theepitaxial substrate. However, with a luminescent device 40 actuallyfabricated, this epitaxial substrate is removed, and a supportingsubstrate 12 which is different from the epitaxial substrate isconnected on the side opposite to the side where the epitaxial substratehas been given.

FIG. 2 is a flowchart showing the steps of manufacturing a luminescentdevice according to the present embodiment of the present invention.FIG. 3 (a)-(f) and FIG. 4 (g)-(i) are sectional views of a substrate inthe respective steps of the method for manufacturing a luminescentdevice according to the present embodiment of the present invention.Herein, the case where, as this luminescent device, a light-emittingdiode (LED) made of a gallium nitride based material is manufacturedwill be described. This LED is a laminate of an n-type layer, aluminescent layer, and a p-type layer, and in FIG. 1 (a)-(b), astructure of one device of an LED is shown, however, actually, aplurality of LEDs can be formed on a single supporting substrate, andafter formation of a plurality of devices, these can be separated intoindividual devices, or can be connected in series or parallel for use.

The method of manufacturing a semiconductor device according to thepresent embodiment has a compound semiconductor layer formation step(step S31), a device region formation step (step S32), a sacrificingportion formation step (step S33), a covering step (step S34), a windowformation step (step S35), a foundation layer formation step (step S36),a plating step (step S37), a covering layer removing step (step S38), achemical lift-off step (step S39), a sacrificing portion removing step(step S40), an n-type electrode formation step (step S41), and a wirebonding step (step S42).

In the compound semiconductor layer formation step (step S31), alift-off layer (a metal buffer layer) and a compound semiconductor layeron the lift-off layer are formed on an epitaxial substrate. First, asshown in FIG. 3 (a), a lift-off layer 21 is formed on an epitaxialsubstrate 20. As the epitaxial substrate 20, an MN template substrate (asubstrate having an AlN layer on a surface of sapphire) is particularlypreferably used. In addition, as the lift-off layer thereon, scandium(Sc) or chrome (Cr) can be used, for example. Film formation of thelift-off layer 21 can be performed by the sputtering method, the vacuumevaporation method, or the like.

Next, in this state, by making such a nitriding treatment as heating inan ammonia atmosphere, the lift-off layer 21 is nitrided to be ascandium nitride layer (a metal nitride layer: ScN layer) or a chromenitride layer (a metal nitride layer: CrN layer). Hereinafter, the casewhere Sc (an ScN layer) is used for the lift-off layer 21 will be citedas an example for explanation.

Next, on the lift-off layer 21, an n-type GaN layer (n-typesemiconductor layer: n-type layer) 11 a, a luminescent layer 11 b, and ap-type GaN layer (p-type semiconductor layer: p-type layer) 11 c aresequentially deposited (an epitaxial growth step). This film formationis performed by, for example, the metal organic chemical vapordeposition process (MOCVD process), an impurity serving as a doner beingdoped into the n-type layer 11 a, while an impurity serving as anacceptor into the p-type layer 11 c.

In the device region formation step (step S32), at least part of thecompound semiconductor layer (laminate) 11 is removed by etching to forma device region 11 d and a separation groove 22 concurrently (FIG. 3(b)). As shown in FIG. 3 (b), the separation groove 22 has a depthranging from the upper side (the p-type layer 11 c side) in FIG. 3 tothe surface of the epitaxial substrate 20. Thereby, the laminate 11 isdivided on the substrate 20. In FIG. 3 (b), a section in one directionis shown, however, this separation groove 22 is also formed in adirection different therefrom, a device region 11 d surrounded by theseparation groove 22 being formed in a plurality of regions. Thereby, anetchant for chemical lift-off can be supplied to the lift-off layer inthe respective device regions. The device region 11 d is preferablycircular. This is because, at the time of etching in the chemicallift-off process, the region which is not yet dissolved is uniformlyreduced in size, and initiation of cracks due to the stressconcentration in the circumferential portion of the device region can besuppressed. The lines used for device separation is preferred to be madeto form polygonal shape, particularly preferably quadrangular shape.This is because such a geometry facilitates device separation by dicing,or the like, and is used for formation of a sacrificing portion.

Formation of the separation groove 22 is performed in the following way,for example. SiO₂ is deposited on the compound semiconductor layer 11 bythe CVD process; a resist is used to perform patterning; and etching ismade with BHF to form a mask of SiO₂. Thereafter, using SiO₂ as a mask,the compound semiconductor layer is dry-etched until the epitaxialsubstrate is exposed. Thereafter, BHF is used to remove the SiO₂ mask.

Next, on the entire face of the p-type layer 11 c located at theuppermost face, a material which can make an ohmic contact with thep-type layer 11 c is deposited as a p-side electrode 23. For example,Ni/Au (50 Å/200 Å) is deposited by sputtering or deposition, andannealed.

In the sacrificing portion formation step (step S33), a sacrificingportion 42 which is formed of a material which will not be removed inthe chemical lift-off step, and has a level lower than the surface ofthe semiconductor layer 11 is formed around the device region on theepitaxial substrate 20. As the material of the sacrificing portion 42,any material which can secure the adherence to the epitaxial substrate20 and the later-formed foundation layer 14, will not be removed in thechemical lift-off step, and can be easily removed without having anadverse effect on the others after the chemical lift-off step can beused, and for example, chrome (Cr) or silicon dioxide (SiO₂) can beused.

The area around the device region on the epitaxial substrate 20 is anarea which is not continuous to the device region on the epitaxialsubstrate exposed by the separation groove 22, and is required to bedisposed discontinuously and independently in a location symmetricalwith respect to the device region. This is because, if the sacrificingportion 42 closes up the lift-off layer 21 from the outside, the pathfor inflow of the etchant in the chemical lift-off step is blocked,thereby the chemical lift-off taking more time, resulting in theproductivity being deteriorated.

In the covering step (step S34), it is preferable to cover the epitaxialsubstrate 20, the semiconductor layer 11, and the sacrificing portion 42to form a covering layer 24 such that the level of the surface thereofin the region away from the device region is lower than the surface ofthe luminescent layer 11 b (FIG. 3 (c)). As the covering layer 24, it ispreferable to use a photoresist which allows the aforementioned geometryto be obtained according to the coating conditions, and which can beeasily dissolved and removed.

By making the level of the film surface lower than the surface of theluminescent layer 11 b with the epitaxial substrate side being directeddownward, the level of the side face 13 b of the reflection layer 14after the upside-down reversal in the chemical lift-off step is higherthan the luminescent layer 11 b in the region away from the deviceregion with the supporting substrate side being directed downward.Thereby, the emitted light directed from the active layer toward ahorizontal direction is reflected at the side face 13 b to permit it tobe taken out in a vertical direction. In the figure, the area which hasthe sacrificing portion is used for explanation, however, also in thearea which has no sacrificing portion, it is preferable to form acovering layer 24 such that the level of the surface of the coveringlayer 24 in the region away from the device region is lower than thesurface of the luminescent layer 11 b. In other words, it is preferablethat, after separating the device region as an individual device, thelevel of the side face 13 b of the reflection layer 14 surrounding theactive layer of the device region be higher than that of the luminescentlayer 11 b throughout the entire angle of 360 deg in a horizontaldirection of the active layer with the supporting substrate beingdirected downward.

In the window formation step (step S35), the covering layer 24 on thesemiconductor layer 11 and that on the surface of the sacrificingportion 42 are removed to form a window 25 and a window 43 (FIG. 3 (d)).This window formation step (step S35) is performed by thephotolithography if the covering step uses a photoresist. Any method maybe used, provided that it can cover the epitaxial substrate as describedabove, except part on the semiconductor layer and on the sacrificingportion, and the window formation step and the covering step may behandled as a covering step without differentiating them as in thepresent embodiment.

In the foundation layer formation step (step S36), a foundation layer 14is formed on the surface of the covering layer 24 and the surface of thesemiconductor layer 11 (including the surface of the p-side electrode23), and on the sacrificing portion 42. The foundation layer has a goodadherence to the semiconductor layer 11 and the sacrificing portion 42,and plays a role of a seed in the plating process. It is preferable thatthe semiconductor side of the foundation layer be not etched by therespective etchant for the covering layer, the lift-off layer, and thesacrificing portion. Further, in the case where the foundation layer 14is to be provided with a reflection function for light from theluminescent layer, it can be comprised of a seed layer 14 a and areflection layer 14 b; the surface on the semiconductor layer side ofthe reflection layer 14 b in that case may be formed of a platinum groupmetal, such as rhodium or ruthenium; and in the foundation layerformation step (step S36), the reflection layer 14 b and the seed layer14 a can be formed from the semiconductor layer side in this order (FIG.3 (e)). As the seed layer 14 a, it is preferable that, in the case whereNi plating is to be used in the subsequent plating step, palladium (Pd)be used for the surface on the plating side, while, in the case where Cuplating is to be used in the subsequent plating step, Pt/Cu be used forthe surface on the plating side. Part of the foundation layer 14 thathas formed a bonding to the sacrificing portion 42 provides a convexportion 41.

In the plating step (step S37), a supporting substrate 12 is formed byproviding plating on the reflection layer 14 (FIG. 3 (f)). Any platingmetal may be used, provided that it can be plated, and is different fromthe lift-off layer and the sacrificing portion, and it is preferable touse Ni plating or Cu plating. The plating process may be of dry type orwet type.

In the covering layer removing step (step S38), the covering layer 24 isremoved (FIG. 4 (g)). By soaking in the photoresist remover, the gapbetween the semiconductor layer 11 and the epitaxial substrate 20 thatis closed up by the covering layer 24 is recovered to form a path forinflow of the etchant in the later chemical lift-off step. Anyphotoresist remover may be used, provided that there is no adverseeffect at least on the sacrificing portion, or the like; the photoresistremover is selected according to the type of the photoresist; and anorganic solvent, such as acetone, or the like, can be utilized.

In the chemical lift-off step (step S39), the semiconductor layer 11 andthe epitaxial substrate 20 are separated from each other (FIG. 4 (h)).The chemical lift-off step (step S39) performs chemical etching bysoaking the substrate 50 formed by plating in, for example, hydrochloricacid for performing chemical etching to dissolve the lift-off layer 21(FIG. 4 (h)). In this chemical lift-off step (step S39), thesemiconductor layer 11 can be peeled off from the epitaxial substrate 20such that no cracks are initiated, because the convex portion 41 of theside face and the sacrificing portion 42 are bonded to be like a column,thereby the deformation on the epitaxial substrate side and thesemiconductor layer side being suppressed and the stresses imposed onthe semiconductor layer being relieved, even if the portion which hasnot yet been dissolved is reduced in size by etching the lift-off layer21.

The sacrificing portion removing step (step S40) uses a selectiveetchant for Cr (cerium ammonium nitrate), for example, in the case wherethe sacrificing portion is Cr, and BHF (buffered hydrofluoric acid), forexample, in the case where the sacrificing portion is silicon dioxide(SiO₂) for performing chemical etching to thereby dissolve thesacrificing portion 42 for peeling off the epitaxial substrate 20. Sincethe semiconductor layer has already been separated by the chemicallift-off, the sacrificing portion which maintains bonding can bemechanically peeled off, however, use of etching makes it difficult foran unnecessary deposit to occur, thus it is desirable to use etching.

After the sacrificing portion removing step, by passing through then-type electrode formation step (step S41), a device separation step(not shown) by dicing, or the like, with the device separation scheduledline, and the wire bonding step (step S42), a vertical type LED(semiconductor device) which allows the light to be effectively takenout can be manufactured. It is more preferable to form a protection filmwhich covers the entire device region except on the n-type electrode.This is for preventing occurrence of a leak between the side face 13 bof the supporting substrate and the semiconductor layer.

The aforementioned embodiment has been explained using an AlN templatesubstrate as the epitaxial substrate 20, however, as the epitaxialsubstrate 20, besides the AlN template substrate, any other material,such as sapphire, SiC, or the like, can be used, provided that it allowsa good-quality group III nitride semiconductor (the n-type layer 11 a,the luminescent layer 11 b, the p-type layer 11 c), such as GaN or AlN,AIGaN, BAlInGaN, or the like, to be grown through the buffer layer 21,or the like. A similar group III nitride substrate may be used, however,using a dissimilar material, such as sapphire, SiC, or the like, whichgenerates less internal stress, is particularly effective as a way ofcontrolling the internal stress in the case where lift-off is to beperformed using an epitaxial substrate which generates internal stressbetween it and a semiconductor layer to be grown, in other words, adissimilar epitaxial substrate.

The aforementioned example was explained on the assumption that thelaminate is constituted by the n-type layer 11 a, the luminescent layer11 b, and the p-type layer 11 c which are all formed of a GaN basedmaterial. However, it is obvious that, even in another case, the sameadvantages are obtained. For example, it is also obvious that asemiconductor device, such as an HEMT, a diode utilizing a simple pnjunction, a light-emitting diode (LED), in which a luminescent layer(active layer) is provided between an n-type layer and a p-type layer,and a laser diode can be manufactured in the same manner. In addition,the n-type layer and the p-type layer may be made of another group IIInitride substrate, for example, Al_(a)In_(b)Ga_(1-a-b)N (0≦a≦1, 0≦b≦1,a+b≦1), in place of GaN. In the case of a luminescent device, in theepitaxial growth step, the n-type layer 11 a, the active layer, and thep-type layer 1 is are formed in this order, for example.

In the aforementioned embodiment, explanation was made using Sc as thelift-off layer 21 in the compound semiconductor layer formation step(step S31), however, in the case where Cr is used as the lift-off layer21, for example, sodium per manganate, potassium permanganate, or thelike, can be used as the lift-off layer etchant which is to be used inthe chemical lift-off step (step S39). At that time, as the sacrificinglayer 42 in the sacrificing portion formation step (step S33), SiO₂ canbe used in place of Cr. And at that time, as the sacrificing layeretchant which is to be used in the sacrificing portion removing step(step S40), BHF can be used. Thus, according to the type of the lift-offlayer 21, the type of sacrificing layer and etchant that allows bondingto be maintained without being etched in the chemical lift-off step isselected.

Example

On the face of an AlN (0001) template substrate which has been obtainedby growing an AlN single crystal layer (having a thickness of 1 μm) onsapphire using the MOCVD process, scandium (Sc) was deposited by thesputtering method to a film thickness of 100 Å as a lift-off layer.

Next, in the ammonia atmosphere, nitriding treatment was performed at1200° C. for 10 minutes, thereby the lift-off layer was nitrided, ascandium nitride layer (ScN layer) being formed.

Next, on the ScN layer, non-doped AlGaN of 2 μm, a Si-doped n-type AlGaNlayer (1.5 μm), an MQW active layer (0.1 μm), and a Mg-doped p-typeAlGaN layer (0.3 μm) were sequentially deposited by the MOCVD process.

SiO₂ was deposited on the p-type AlGaN layer by the CVD process; aresist was used for patterning; with BHF, etching was performed to forma SiO₂ mask; and the compound semiconductor layer was dry-etched untilthe AlN template substrate was exposed.

Thereafter, BHF was used to remove the SiO₂ mask; a circular deviceregion having a diameter of 850 μm was formed. Next, on the p-type layerin the device region, Ni/Au. (50 Å/200 Å) was deposited as a p-sideelectrode, and annealed at 550° C. for 15 minutes.

In the sacrificing layer formation step, a Cr (200 Å) layer having adiameter of approx. 95 μm was formed at the four corners as asacrificing layer, being spaced away from the device region on the AlNtemplate substrate which has been exposed by dry etching.

In the covering layer formation step, a photoresist was spin-coated as acovering layer, and patterning was performed such that the device regionand the sacrificing layer were exposed. The exposed portion in thedevice region has a diameter of 840 μm, and the sacrificing layer has adiameter of 90 μm. The thickness of the photoresist which was left onthe circumference of the sacrificing layer after the patterning wasapprox. 2 μm, and the level of the photoresist surface from theepitaxial substrate was lower than that of the active layer.

On the covering layer, and on the exposed device region and sacrificinglayer, Pt/Au/Pt/Pd (250 Å/5500 Å/250 Å/150 Å) was deposited in thisorder as a foundation layer by the sputtering method. Thereafter, on thefoundation layer, Ni plating was performed using a. commerciallyavailable Ni electroless plating fluid to form a Ni supporting substratehaving a thickness of 100 μm from the flat bottom portion.

In the covering layer removing step, the photoresist of the coveringlayer was removed by soaking it in acetone.

In the chemical lift-off step, the epitaxial substrate and thesemiconductor layer were separated from each other. By soaking thelift-off layer in hydrochloric acid for 24 hr, the chemical etching ofit was performed, and by removing the lift-off layer, the AlN templatesubstrate and the semiconductor layer were separated from each other. Inthis chemical lift-off step, the sacrificing layer is not removed by theetchant, and thus the connection between the AlN template substrate andthe Ni supporting substrate was maintained through the sacrificing layerand the foundation layer.

After the chemical lift-off step, in the sacrificing layer removingstep, the sacrificing layer was soaked in a cerium ammonium nitratesolution to etch away it to separate the supporting substrate(foundation layer) and the AlN template substrate from each other.

Comparative Example

Operations were carried out as in Example, except that no sacrificinglayer was formed, and in the covering layer formation step, patterningof the photoresist was performed such that only the device region wasexposed. In the chemical lift-off step, the supporting substrate and theAlN template substrate were separated from each other, the sacrificinglayer removing step being not provided.

The quality of the compound semiconductor layer after peeling off the MNtemplate substrate in Example and that in Comparative Example werecompared with each other by surface observation with an opticalmicroscope. In Comparative Example as shown in FIG. 5, after thesubstrate peeling off, it was observed with a metallurgical microscopeand an electron microscope that, with nine of the ten samples, thereinitiated cracks in the central portion of the compound semiconductorlayer after the AlN template substrate peeling off. It can be supposedthat the compound semiconductor layer was etched from thecircumferential portion, and in a miniature region left in the centralportion just before the AlN template substrate was peeled off, thereoccurred a stress concentration between the substrate and the compoundsemiconductor layer and supporting substrate, thereby after the peeling,cracks were observed. However, in Example, as shown in FIG. 5, cracks asin Comparative Example were not observed in the compound semiconductorlayer. It can be supposed that the sacrificing layer portion, whichplays a role as a column between the epitaxial substrate and thesemiconductor layer in the chemical lift-off step, suppresses thedeformation, thereby the stress imposed on the semiconductor layer onthe device region side surrounded by the columns is greatly alleviatedin comparison with Comparative Example, thereby cracks are preventedfrom being initiated on the device region side. Therefore, it was foundthat, in Example, no cracks will be caused at the time of AlN templatesubstrate peeling-off, and in the compound semiconductor layer, which isto be lifted-off by etching the lift-off layer from the periphery,occurrence of cracks can be suppressed in a place where stresses wouldbe concentrated as the etching is progressed.

In addition, with the samples prepared in Example and ComparativeExample, part of the non-doped AlGaN layer in the peeled-off compoundsemiconductor layer was further dry-etched to be removed in the rangerequired for formation of n-type electrode, and Ti/Al was formed in thisorder on the exposed n-type AlGaN layer to form an n-type electrode, andan I-V measurement was made using a constant current voltage measuringinstrument. At a reverse voltage Vr (−10 μA), Example exhibited over 10V, while, the samples with which cracks were observed in ComparativeExample as low as approx. 6 V. It can be supposed that, in. ComparativeExample, occurrence of cracks increased the leakage current. Thus it hasbeen found that, in accordance with the present invention, ahigh-quality luminescent device exhibiting a smaller leakage current canbe obtained.

The structure, geometry, size and positional relationship as explainedin the aforementioned embodiment have been only schematically given tosuch a degree that the present invention can be understood andimplemented, and the numerical values and the composition, and the like,of each structure have been only exemplified. The technique whichprevents occurrence of cracks at the time of chemical lift-off is anecessary technique for not only the luminescent device, but also forthe whole types of semiconductor devices. Therefore, the presentinvention is not limited to the embodiment which has been explained, andmay be modified to various forms so long as there is no departure fromthe range of the technical concept as given in the scope of claim forpatent.

However, in order to implement the present invention, it is necessary toobtain, from among the limited number of materials which can be used asa semiconductor device, the material composition of the presentinvention that meets the requirements for each selective etching fluidand the resistance to the etching fluid.

INDUSTRIAL APPLICABILITY

The luminescent device and the method for manufacturing a luminescentdevice and a semiconductor device in accordance with the presentinvention are applicable to LED optical devices and methods formanufacturing LED optical devices.

DESCRIPTION OF SYMBOLS

-   11: Semiconductor layer-   11 a: n-type GaN layer (n-type semiconductor layer: n-type layer)-   11 b: Luminescent layer-   11 c: p-type GaN layer (p-type semiconductor layer: p-type layer)-   12: Supporting substrate-   13: Concave portion-   13 a: Flat bottom face (flat portion)-   13 b: Tapered side face-   14: Foundation layer-   14 a: Seed layer-   14 b: Reflection layer-   20: Epitaxial substrate-   21: Lift-off layer-   22: Separation groove-   23: p-side electrode-   24: Covering layer-   40: luminescent device-   42: Sacrificing portion

What is claimed is:
 1. A manufacturing method for a semiconductordevice, comprising: a device region formation step of forming a deviceregion constituted by a semiconductor layer on part of an epitaxialsubstrate through a lift-off layer; a sacrificing portion formation stepof forming a sacrificing portion, being not removed in a later-mentionedchemical lift-off step, around the device region on the epitaxialsubstrate; a covering step of forming a covering layer that covers theepitaxial substrate while leaving exposed at least part of thesemiconductor layer and at least part of the sacrificing portion; afoundation layer formation step of forming a foundation layer on asurface on the epitaxial substrate including part on the semiconductorlayer and on the sacrificing portion and a covering layer surface; aplating step of forming a supporting substrate by providing plating onthe foundation layer; a covering layer removing step of dissolutionremoving of the covering layer; a chemical lift-off step of separatingbetween the semiconductor layer and the epitaxial substrate bydissolution removing of the lift-off layer; and a sacrificing portionremoving step of separating between the epitaxial substrate and thefoundation layer at the sacrificing portion after the chemical lift-offstep.
 2. A manufacturing method for a luminescent device including asemiconductor layer having a luminescent layer, comprising: a deviceregion formation step of forming a device region constituted by thesemiconductor layer on part of an epitaxial substrate through a lift-offlayer; a sacrificing portion formation step of forming a sacrificingportion, being not removed in a later-mentioned chemical lift-off step,around the device region on the epitaxial substrate; a covering step offorming a covering layer that covers the epitaxial substrate whileleaving exposed at least part of the semiconductor layer and at leastpart of the sacrificing portion; a foundation layer formation step offorming a foundation layer on a surface on the epitaxial substrateincluding part on the semiconductor layer and on the sacrificing portionand a covering layer surface; a plating step of forming a supportingsubstrate by providing plating on the foundation layer; a covering layerremoving step of dissolution removing of the covering layer; a chemicallift-off step of separating between the semiconductor layer and theepitaxial substrate by dissolution removing of the lift-off layer; and asacrificing portion removing step of separating between the epitaxialsubstrate and the foundation layer at the sacrificing portion after thechemical lift-off step.
 3. The manufacturing method for a luminescentdevice of claim 2, wherein, in the device region formation step, thesemiconductor layer includes an n-type layer, a luminescent layer, and ap-type layer, being constituted by a group III nitride semiconductor, inthis order from a top surface of the epitaxial substrate side, on whichthe semiconductor layer is formed.
 4. The manufacturing method of claim2, wherein, in the covering step, a photoresist is coated for making acovering such that the level of the covering layer surface from theepitaxial substrate at least on the sacrificing portion is lower thanthe luminescent layer, and part of the covering layer on thesemiconductor layer and the sacrificing portion is removed byphotolithography.
 5. The manufacturing method of claim 4, wherein, inthe foundation layer formation step, the foundation layer includes areflection layer on the semiconductor layer.
 6. A luminescent devicemanufactured by the manufacturing method for a luminescent device ofclaim 2.